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111.
Gillespie J.K. Fitch R.C. Sewell J. Dettmer R. Via G.D. Crespo A. Jenkins T.J. Luo B. Mehandru R. Kim J. Ren F. Gila B.P. Onstine A.H. Abernathy C.R. Pearton S.J. 《Electron Device Letters, IEEE》2002,23(9):505-507
The low temperature (100°C) deposition of Sc2O3 or MgO layers is found to significantly increase the output power of AlGaN/GaN HEMTs. At 4 GHz, there was a better than 3 dB increase in output power of 0.5×100 μm2 HEMTs for both types of oxide passivation layers. Both Sc2 O3 and MgO produced larger output power increases at 4 GHz than conventional plasma-enhanced chemical vapor deposited (PECVD) SiNx passivation which typically showed ⩽2 dB increase on the same types of devices. The HEMT gain also in general remained linear over a wider input power range with the Sc2O3 or MgO passivation. These films appear promising for reducing the effects of surface states on the DC and RF performance of AlGaN/GaN HEMTs 相似文献
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115.
酶促合成生物柴油反应动力学 总被引:1,自引:0,他引:1
以Candidasp.99-125脂肪酶为催化剂,甘油三油酸酯和甲醇为底物,采用有序机制模型对酶促合成生物柴油的酯交换反应动力学进行了研究,并与经典乒乓机制模型进行了比较。研究结果表明,反应初速率的实验值与有序机制模型方程的计算值吻合很好。对于固定化Candidasp.99-125脂肪酶催化合成生物柴油的酯交换反应机理进行研究,采用有序机制模型比经典乒乓机制模型更为精确。反应过程中,醇抑制为竞争性抑制,在甘油三油酸酯浓度较小的范围内,醇抑制作用较为显著,醇浓度越低反应初速率越快。该有序机制模型可用来预测生物柴油的生产批次或连续反应器中酯交换反应的速率,确定最佳底物油脂和醇的浓度。 相似文献
116.
M Sandoval PR Henry XG Luo RC Littell RD Miles CB Ammerman 《Canadian Metallurgical Quarterly》1998,77(9):1354-1363
Four experiments were conducted to identify several factors that might improve the accuracy and reproducibility of Zn bioavailability assays for chicks. Response of tissue Zn and metallothionein (MT) concentrations to various elevated levels and soluble sources of dietary Zn were measured, as well as the effect of delaying high Zn administration until 7 d posthatching to alleviate the detrimental effect of Zn sulfate on feed intake to 3 wk of age. Bone Zn increased (P < 0.01) in all experiments in response to increasing dietary Zn concentrations. Liver and pancreas MT were affected (P < 0.01) by a source by age interaction and variability that made this criterion unsuitable for bioavailability assays. Lastly, 1-d-old chicks were used to study the effect of delaying feeding of a high-Zn diet up to 7 d of age. The basal diet was fed continuously for 21 d as a control. A diet containing 1,000 ppm Zn was either fed continuously from Day 1, or started on Day 3, 5, or 7. Chicks given high Zn on Day 3, 5, or 7 decreased (P < 0.01) feed intake within 24 h of feeding. Delayed feeding of high dietary Zn might help to alleviate decreased feed intake observed in previous studies. Delaying the onset of high Zn feeding by several days may help alleviate feed intake problems observed with Zn sulfate. Use of either Zn gluconate or Zn acetate as a standard in assays or use of MT synthesis as a bioavailability criterion will probably not be useful to improve accuracy of the estimates. 相似文献
117.
云纹图象计算机处理技术的进展及其应用 总被引:2,自引:0,他引:2
本文对1987年至今国内外光测力学条纹图,主要是云纹图象的计算机采集,处理和力学量提取技术的进展进行了回顾,包括利用通用图象处理程序,直接利用灰度,用付利叶变换对条纹图进行分析,引入相移技术提高灵敏度,利用采色编码提取力学量。以及建立在云纹图特点基础上的新的图象处理技术等;分析了它们各自的优缺点,适用范围和存在的问题,讨论了它们在科究和工程测试中的应用前景。 相似文献
118.
Q Wang S Zhong J Ouyang L Jiang Z Zhang Y Xie S Luo 《Canadian Metallurgical Quarterly》1998,(348):259-268
Culture selected and expanded osteoblastic cells may be able to be reintroduced into massive skeletal defects to accelerate cell mediated regeneration of skeletal tissues, especially in bone ingrowth in total joint replacement, fracture healing, and osteoporosis. In vitro osteogenic cell culture is a useful model in studying the mechanism of bone metabolism under direct current stimulation. In this study, an osteoblastlike cell line was isolated from newborn rat calvaria. The osteogenic processes of the in vitro cultured cell line were studied by cytochemical, electron microscopic, and energy dispersive x-ray analysis techniques that resembled those observed in membrane bone ossification centers in vivo. Direct current stimulation of 100 microA/cm2 accelerated greatly the proliferation and calcification of the in vitro cultured cells. Intracellular free calcium ion metabolism was measured with an Adherent Cell Analysis and Sorting Machine. Under direct current stimulation, intracellular free calcium ion concentration increased an average of 2.3 times of the original level, which may play a key role in regulating osteogenesis and bone metabolism. 相似文献
119.
A micellar electrokinetic capillary chromatographic (MECC) method has been developed and optimised for the separation of 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG). The running buffer consisted of a mixture of 20 mM sodium phosphate and 20 mM sodium borate containing 50 mM sodium dodecyl sulphate (SDS) adjusted to pH 9.5 with 1 M NaOH. The running voltage and temperature were 20-25 kV and 30 degrees C, respectively. The MECC method for the analysis of PBG is fast and simple and is useful for the screening of PBG in the urine of patients suspected to have acute intermittent porphyria (AIP), and for the confirmation of lead exposure by measuring red-cell ALA-dehydratase (ALA-D) activity with ALA as the enzyme substrate. 相似文献
120.